Typically, security screening systems in airports make use of devices generating penetrating radiation, such as x-ray devices, to scan individual pieces of luggage to generate an image conveying the contents of the luggage. The image is displayed on a screen and is examined by a human operator whose task it is to detect and possibly identify, on the basis of the image, potentially threatening objects located in the luggage.
A deficiency with conventional security screening systems is that the job of luggage screening can become repetitious, leading to lapses in attention during which potentially dangerous items may be inadvertently allowed on board an aircraft for example.
In order to alleviate at least in part the above described deficiency, luggage screening systems are sometimes equipped with threat image projection (TIP) systems adapted for displaying an image of a piece of luggage with a simulated threat appearing thereon.
These threat image projection (TIP) systems allow merging two images: one image of a threat (e.g.: handgun, gun part, knife, improvised explosive device, etc.) based on stored images with one “live” image of a piece of luggage passing on the belt of the screening systems (such as an x-ray machine). The combined image is then displayed on the usual security screening monitor to the luggage screener who is then expected to process the luggage in accordance with the usual procedure when an actual threat is detected in the luggage. The functionality of such threat image projection systems is used during normal operation for benchmarking purposes, to keep luggage screeners alert, for maintaining the proficiency of experienced users and for training new users. An example of such a system is described in U.S. Pat. No. 6,899,540 issued to Neiderman, et al. on May 31, 2005 and entitled “Threat Image Projection System”. The contents of the above referenced document are incorporated herein by reference. In Neiderman et al., a computer system which causes a luggage screening monitor to show computer-generated (i.e. simulated) contraband items in a piece of luggage is described. This is done by either overlaying a computer-generated image of a contraband or other item onto the image of the luggage being screened, or by substituting the image of an entire piece of luggage which contains contraband for the image of the luggage being screened. The system also checks whether the contraband item (threat) fits into the current luggage being screened in order to ensure that a large threat is not projected into a small bag (e.g., a purse), thus cueing the screener that the threat is simulated. If the system determines that the selected contraband item (threat) does not fit in the luggage, the simulated contraband item is not displayed.
A deficiency in systems of the type described above is that the images shown to the user containing the computer-generated (i.e. simulated) contraband item (e.g. threat) do not convincingly convey that what the user is looking at is a real contraband item in the piece of luggage being screened. Frequently, the manner in which the images are merged together leads screeners to conclude that the threat displayed in the image of the piece of luggage was computer-generated as the result of the threat image projection (TIP) image-merging feature rather than a real threat.
Consequently, there is a need in the industry for providing a method and system for performing threat image projection (TIP) that alleviate at least in part the deficiencies of the prior art.